In my experience, dr farts is the result of an overabundance of options and lack of foresight. They don’t know what it’d be like, so they try it. Giving players a silly character swap voucher, good for just one session per campaign, solves that. Similar deal for the overjuiced character. (Not usable during story boss encounters)

Once people recognize that the boundaries are there to improve their experience, not detract from it, they usually follow the flow of the game and build on others’ characters. If they don’t, chairs are easy to fill.